It is known to provide, along the face of a building to be renovated or at a construction site at which a building or other structure is to be erected, a so-called construction or service elevator which generally comprises a mast moored to the side of the building and having a pair of rails on which a cabin is guided by respective rollers, the cabin being raised and lowered by a hoist mechanism or a rack and pinion arrangement.
Such elevators can deliver building materials at the various levels, can be used as personnel transporters and can even be employed to remove construction detritus from the various levels.
In earlier elevator constructions of this type, the mast is assembled by stacking a number of units, each of which may form the mast at a respective level and consists of tubular elements welded together. The rail forming members are generally rectangular-section tubes also welded in place on these units.
Means is provided at the bottom of one such unit and the top of an underlying unit to connect the two units together and interfitting formations are provided on the rail pieces to assure proper alignment.
Not only are such structures expensive because complete preformed units for each level of the mast are required, but they frequently lack the desired stability because between vertically adjoining units, weak zones are formed over the full cross section of the mast and may fail if, for some reason, the connections are inadequate or are subject to fatigue.
Furthermore, if one of the units is found to be defective in manufacture as it is hoisted into place, significant problems with assembly ensue and a correction may not be simple or may result in weakening of the entire structure.
Problems are also encountered because of the need to have interfitting tenon-like connections between the tubular members forming the rails.